1. Field of Invention
This invention relates to the field of prosthetics, specifically to prosthetic ankle joints.
2. Description of Prior Art
In the last 100 years, the field of prosthetics has experienced a slow evolution from being an anecdotal craft to a legitimate medical profession. As one might expect, the components used in the field have undergone an equal form of evolution as new science, theory and materials have entered the profession. Of the evolving mechanisms, the prosthetic ankle joint has assumed many different shapes, designs and compositions as the most accurate solution to a suitable prosthetic replacement for the lost human ankle has been sought.
Existing lower extremity prosthetic ankle/foot systems tend to simulate more than replicate the motions that a normal human ankle experiences throughout the gait cycle. In U.S. Pat. No. 4,506,395 to Haupt (1985), the motion of plantarflexion in a prosthetic system is simulated only by the compression of a low durometer foam in a prosthetic foot which manipulates weight line positions rather than kinematically accurate changes in foot position. U.S. Pat. No. 6,129,766 to Johnson, et al. (2000), discloses an ankle joint design which incorporates a set of bumpers to limit ankle motion. An additional design found in U.S. Pat. No. 4,959,073 to Merlette (1990), simulates ankle motion through the deformation of an entire foot and ankle segment.
There remains a terrific need for a prosthetic ankle joint that seeks to accurately replicate the function and timing of normal muscle activity throughout the gait cycle. Although existing designs may allow for some ankle motion for the prosthetic user, most of the foot/ankle components are very limited in their functional motion and adjustability and require greater than normal forces to actuate. There is no current foot/ankle system which allows its function to be fine tuned to each patient to maximize the normal motions experienced not only through the gait cycle, but through their general activities of daily living as well.
Previous prosthetic ankle designs also fall short of maximizing a patient""s function because they do not allow for any critical angular adjustments to improve functional ankle control or to address indiviual alignment concerns. The design of most prosthetic ankles or foot/ankle combinations, also restricts the pt. from wearing a variety of different shoes with varying heel heights and usually limit the amputee to the use of one type of prosthetic foot.
In accordance with the present invention a prosthetic ankle joint comprises an upper and lower housing that are joined by a common axis and manipulated in space by motion members as well as chamber elements within the upper housing.
Accordingly, besides the objects and advantages of the prosthetic ankle joint described in my above patent, several objects and advantages of the present invention are:
a) To provide an ankle joint which provides the most accurate kinematic replication of foot and ankle relationships during the gait cycle.
b) To provide an ankle joint which allows functional foot motion for the patient in a seated or non-weight bearing position.
c) To provide an ankle joint whose plantarflexion activation threshold can be fine-tuned for different activities by the prosthetist or the user.
d) To provide an ankle joint that is fully adjustable to accommodate a variety of different shoe heel heights worn by the user.
e) To provide an ankle joint that can be aligned and adjusted by a prosthetist to maximize the performance of a selected prosthetic foot.
f) To provide an ankle joint which is adapted to fit a multitude of prosthetic feet.
g) To provide an ankle joint which replicates the height of a normal ankle joint.
h) To provide an ankle joint which ultimately limits the quadriceps demand at initial contact by significantly decreasing the knee flexion moment and increasing the plantarflexion response of the foot.
i) To provide an ankle joint which ultimately decreases the overall energy expenditure of the amputee through the implications of a more natural gait.
j) To provide an ankle joint which simulates the eccentric contractions of dorsiflexor muscles upon the foot at initial contact through the deformation of its motion members.
k) To provide an ankle joint which simulates the concentric action of plantarflexor muscles upon the foot during stance through the limitation of upper housing motion by the chamber elements.
l) To provide an ankle joint which simulates the concentric action of the dorsiflexor muscles upon the foot during swing phase through the open-chain response of its motion members.
m) To provide an ankle joint which is completely modular and can be attached to appropriate existing prosthetic componentry both proximal and distal to itself.
n) To provide an ankle joint which is narrow in form to allow for accurate medial-lateral dimensions to be maintained in a cosmetic covering.
o) To provide an ankle joint which has a minimum of moving parts for decreased maintenance requirements.
p) To provide an ankle joint which is resistant to moisture to provide an added degree of freedom to its user.
q) To provide an ankle joint which can be placed in the line of progression of its user to minimize harmful torques during ambulation.
r) To provide an ankle joint which can be cheaply manufactured and provided to a greater patient population due to its affordability.
s) To provide an ankle joint which is functionally appropriate for all existing levels and classifications of patient walking abilities.
t) To provide an ankle joint which has a minimum of components as to increase its ability to assume a lightweight form.